Nuclear tRNA export in trypanosomes: a journey full of twists and turns guided by tRNA modifications.

Zdeněk Paris

doi:10.1017/s0031182021000482

Abstract

Transfer RNAs play a key role in protein synthesis. Following transcription, tRNAs are extensively processed prior to their departure from the nucleus to become fully functional during translation. This includes removal of 5′ leaders and 3′ trailers by a specific endo- and/or exonuclease, 3′ CCA tail addition, posttranscriptional modifications and in some cases intron removal. In this minireview, the critical factors of nuclear tRNA trafficking are described based on studies in classical models such as yeast and human cell lines. In addition, recent findings and identification of novel regulatory loops of nuclear tRNA trafficking in trypanosomes are discussed with emphasis on tRNA modifications. The comparison between the representatives of opisthokonts and excavates serves here to understand the evolutionary conservation and diversity of nuclear tRNA export mechanisms.

Highlights

TRNAs are smaller than the 40 kDa limit for passive diffusion, the export of tRNAs through the nuclear pore complex (NPC) is an active process facilitated by export factors belonging to the karyopherin-β family called exportins
It is well accepted that tRNA subcellular trafficking is not unidirectional from the site of transcription in the nucleus to the cytoplasmic site of protein synthesis
The tRNA retrograde pathway was discovered in yeast, where intron-containing tRNAs travel across the nuclear pore complex to the outer mitochondrial surface where the splicing endonuclease complex is localized (Yoshihisa et al, 2003; Shaheen and Hopper, 2005; Takano et al, 2005)

Summary

Introduction

TRNAs are smaller than the 40 kDa limit for passive diffusion, the export of tRNAs through the nuclear pore complex (NPC) is an active process facilitated by export factors belonging to the karyopherin-β family called exportins. The tRNA retrograde pathway was discovered in yeast, where intron-containing tRNAs travel across the nuclear pore complex to the outer mitochondrial surface where the splicing endonuclease complex is localized (Yoshihisa et al, 2003; Shaheen and Hopper, 2005; Takano et al, 2005).

Results

Conclusion